I guess you are talking about DVDs, right? I guess you want to know this because you are backing up DVDs?
I don't know if there is a program that can detect forced subtitles.
What I do know, is that subs hardly use any space on DVDs, including all subtitles on a DVD shouldn't consume that much that it hurts the image/sound quality (so there's no reason to abandon them).
When there is a forced subtitle on a DVD, it's very often the english subset...